TITLE: GCN CIRCULAR NUMBER: 18974 SUBJECT: Konus-Wind observation of GRB 160131A DATE: 16/02/02 15:36:05 GMT FROM: Anastasia Tsvetkova at Ioffe Institute A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report: The long-duration, extremely hard-spectrum GRB 160131A (Swift-BAT trigger #672236: Page & Barthelmy, GCN 18951; Cummings et al., GCN 18959) triggered Konus-Wind at T0=30044.577 s UT (08:20:44.577). The burst light curve shows a single, FRED-like pulse with a total duration (80-1400 keV) of ~200 s. In the softest KW energy band the emission can be traced up to ~300 s. The emission is seen up to ~15 MeV. As observed by Konus-Wind, the burst had a fluence of 3.26(-0.32,+0.31)x10^-4 erg/cm2, and a 64-ms peak energy flux, measured from T0+2.704 s, of 2.23(-0.46,+0.46)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+162.048 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.97(-0.15,+0.24), the high energy photon index beta = -1.56(-0.10,+0.07), the peak energy Ep = 586(-259,+518) keV, chi2 = 98/97 dof. The spectrum near the peak count rate (measured from T0+0.256 to T0+14.592 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.94(-0.18,+0.13), the high energy photon index beta = -1.56(-0.56,+0.06), the peak energy Ep = 1152(-438,+3060) keV, chi2 = 135/97 dof. Assuming the redshift z=0.972 (Malesani et al., GCN 18965; de Ugarte Postigo, Thoene & Sanchez-Ramirez, GCN 18966; Xu, Xin & Wang, GCN 18969) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~8.3x10^53 erg, the peak luminosity L_iso is ~1.1x10^53 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~1150 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160131_T30044/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.